Hydraulic rate gyro for an adaptive steering system

ABSTRACT

A rate gyro providing a fluidic output signal corresponding to the yaw rate of a vehicle, for use in an adaptive steering system. The gyro rotor is hydraulically supported and spun via tangential reaction jets connected in parallel with flapper nozzles situated to provide both a differential pressure signal corresponding to yaw rate and a centering spring force creating gyro natural frequencies well above the disturbance frequencies encountered. The support, jet, and nozzle fluid supplies are all incorporated into the power steering supply circuit.

United States Patent Kasselmann July 4, 1972 541 HYDRAULIC RATE GYRO FORAN 3,362,233 l/l968 Posingies ..74 5.43 x

ADAPTIVE STEERING SYSTEM 3,435,688 4/1969 Ogren ..74/5.6

3 l 6 69 E 1. ....7 [721 SwmfieldY Mich- 3 232 333 2x370 Rim: [73]Assignee: The Bendix Corporation Primary ExaminerManuel A. Antonakas[22] Flled' March 1970 Attorney-John R. Benefiel and Flame, Hartz, Smith& [21] Appl. No.: 20,962 Thompson [52] [57] ABSTRACT A rate gyroproviding a fluidic output signal corresponding to the yaw rate of avehicle, for use in an adaptive steering system. The gyro rotor ishydraulically supported and spun via [56] References cued tangentialreaction jets connected in parallel with flapper noz- UNTED STATESPATENTS zles situated to provide both a differential pressure signalcorresponding to yaw rate and a centering spring force creating2,133,809 10/1938 Carter 61. al ..74/5.7 X gyro natural frequencies wellabove the disturbance fre uen 3,320,816 1967 Johnstonw X ciesencountered. The support, jet, and nozzle fluid supplies 34 12/1963Parker X are all incorporated into the power steering supply circuit.3,487,701 1/1970 Chang et a1... ..74/5 2,729,106 1/1956 Mathiesen..74/5.7 X 6 Claims, 4 Drawing Figures HYDRAULIC RATE GYRO FOR ANADAPTIVE STEERING SYSTEM BACKGROUND OF THE INVENTION Adaptive steeringsystems have been proposed, in which lateral disturbances imposed on avehicle are automatically compensated for by various controlarrangements, copending U.S. applications, Ser. Nos. 792,238, 792,243,and 792,904, all assigned to the assignee of the present application,disclosing such adaptive steering systems in detail.

These systems, including those disclosed in the US. applicationsreferred to above, usually require some means of sensing the rate ofvehicle yaw and providing a corresponding output signal compatible withthe control system. In the past, aircraft type gyros have been proposedfor this purpose, but these are usually relatively expensive forautomotive applications and may lack sufficient reliability in the lowmaintenance environment encountered in private automobile usage.

In addition, the potential advantages of fluidic controls in these areashas led to the development of fluidic adaptive control systems asdisclosed in the above-referenced applications. In this context, a meansfor producing directly a fluidic output signal indicative of vehicle yawrate would eliminate the need for conversion of the electrical signalsusually produced by the aircraft rate gyros into fluidic signals.

These requirements are met by the vortex rate sensor described in theabove referenced applications, but this device in its present formproduces output signals which require a great deal of amplificationbefore being usable in these systems, hence introducing a complicatingfactor.

Therefore, it is an object of the present invention to provide a simple,reliable, yaw rate sensor which will produce fluidic output signals ofsufficient magnitude that little or no amplification is required forusability in an adaptive steering control system.

SUMMARY OF THE INVENTION This object and others which will becomeapparent upon a reading of the following specification and claims isaccomplished by providing a gyro having a rotor that is hydraulicallysupported, centered, and spun by means of fluid pressure supplied by thepower steering supply circuit, with flapper nozzles similarly suppliedwith fluid pressure disposed adjacent the rotor to provide a rotorcenterforce creating a natural frequency in the yaw mode well above thedisturbances to be created, and to provide a differential pressuresignal indicative of the yaw rate.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view insection of a hydraulic rate gyro according to the present invention.

FIG. 2 is a plan view in section of the hydraulic rate gyro shown inFIG. 1 together with a schematic representation of a fluid supplycircuit.

FIG. 3 is a view of the section taken along the line 3-3 in FIG. 2.

FIG. 4 is a schematic representation of an adaptive control fluidcircuit utilizing the hydraulic rate gyro of the present inventionincorporated into a conventional power steering fluid supply system.

DETAILED DESCRIPTION In the following detailed description certainspecific terminology will be used for the sake of clarity and a specificembodiment described in order to provide a clear understanding of theinvention, but it is to be understood that the invention is not solimited and may be practiced in a variety of forms and embodiments.

Referring to the drawings, and particularly FIGS. 1-3, the hydraulicrate gyro includes a housing 12 within which is supported a rotor 14.

The rotor 14 is pivotally supported by fluid flow through the clearancespaces 16 between the rotor hub 18 and housing end plates 20, 22 formedwith complementary spherical surfaces. This arrangement provides forfluid support while also serving to center the rotor 14, by theBernoulli forces created by the fluid flow through the clearance spaces16.

The fluid is supplied from pressure sources 24, conduit 26, and passage28 communicating with axial opening 30 formed in the rotor hub 18. Fluidflow then occurs through the clearance spaces 16 into the annularopening 32 within the housing 12, hence to outlet port 34 communicatingwith the return of the source 24 via passage 36.

Rotor spin is accomplished by tangential reaction jets 38, 40 (FIG. 3)supplied with fluid via radially extending passages 42, 44 whichcommunicate with axial opening 30. Hence, the bearing and jet flows aresupplied with a parallel fluid connection with axial opening 30, and themagnitude of these flows are not limited by each other, which isparticularly advantageous in this context since the jet flow willordinarily be much stronger than the bearing flow.

The jet flow likewise empties into the annular space 32 to be returnedto the source 24 via conduit 36.

In order to provide a fluidic output signal and to restrain the rotor 14in yaw, a pair of flapper nozzles 46, 48 are positioned in the housingso as to discharge their flow into the periphery of the rotor 14 so asto oppose each other. Fluid for this purpose is supplied via conduits26.

These flapper nozzles 46, 48 are positioned in the yaw plane so as toserve the purposes referred to. Flow efflux therefrom will create aresilient restraining effect on the rotor hub 14, providing theequivalent of a fluid spring. It has been found that the naturalfrequency of the rotor hub 14 in yaw may be controlled by variations inpressure and flow to vary this effective spring rate. Hence, by sosetting the natural frequency of the rotor hub well above that of thefrequency of the lateral disturbances, good response of the rotor 14thereto may be obtained. For a steel rotor two inches in diameter andone-half inch thick spinning at 2,000 rpm, 60 psig, and 1 gpm, supplyflow will produce a natural frequency in yaw of 20 cps, which is wellabove the frequency of lateral disturbances and resultant yawingmovements, usually of the order of l cps.

This arrangement also produces the fluidic output signal. By providingconduits 54, 56 connected to conduits 50, 52 respectively and alsoconnected to a differential fluid amplifier 58, the variations in backpressure created at the flapper nozzles 46, 48 by responsive movement ofthe rotor 14 in response to vehicle yawing movement differentialpressure signals corresponding to the rates of yaw in one direction orthe other are provided at the outputs 60, 62 of the differential fluidamplifier 58. The amplifier 58 may be of conventional design, such asthe dual output jet on jet type of amplifier.

These variations in back pressure are created by slight changes inclearance between the flapper nozzles 46, 48 and the rotor 14 periphery,with yawing movement tending to increase one clearance and decrease theother, depending on the direction of yaw. These signals are notdependent on the precise axial location of rotor 14 with respect to theflapper nozzles 46, 48 inasmuch as the differential back pressure isread at the fluid amplifier.

In order to render the rotor 14 insensitive to angular movements in theother major plane passing through the axis of the rotor 14, a pair ofbearing pads 64, 66 (FIG. 1) are provided in the roll plane. As thespinning rotor 14 approaches either of these, a wedge of dynamicpressure is created by the action of the rotor on the fluid whichsubstantially fills the housing 12 to balance the roll movement responseof the rotor 14 without actual frictional contact.

In operation, fluid pressure from the source 24 causes flow via conduit26 into the opening 30, and thence outwardly to center the rotor 14 inthe housing 12. At the same time fluid flow occurs through passages 42,44 and jets 38, 40 causing the rotor 14 to spin at a high rate of speed.

In the event of yawing movement to the right (as viewed in FIG. 2) thegyroscopic forces will tend to force the rotor 14 nearer the flappernozzle 48 and further away from the flapper nozzle 46. The increase inpressure at nozzle 48 caused by the increase in the restrictive effectof the rotor 14 will then balance these gyroscopic forces, precludingfurther movement. Since the magnitude of the gyroscopic forcesdepends onthe rate of yawing movement, this pressure will likewise vary with therate of yawing movement.

Inasmuch as this basic phenomenon involved in flapper nozzlearrangements is well known in the prior art, it is not felt necessary toexplain this in greater detail.

This increase in pressure at flapper nozzle 48 is accompanied by adecrease in pressure at flapper nozzle 46, due to the increasedclearance and resultant lessening of the restrictive effect on flow bythe rotor 14.

1 These pressures are read at the fluid amplifier 58 to produce fluidoutput signals at 60, 62 the difference in which corresponds to themagnitude of the pressure differential between the flapper nozzles 46,48 hence, providing a fluidic output signal indicative of yaw rate.

As soon as yawing movement ceases, the gyroscopic forces are abated,leading to equilization of the nozzle clearances and pressures, thuseliminating the pressure signal at 60.

Yawing movement to the left creates the reverse situation, leading tothe generation of signals in outlets 60, 62, the difference in whichcorresponds to the magnitude of the rate of yawing movement.

FIG. 4 shows in schematic form the incorporation of this gyro into apower steering supply circuit.

The power steering supply pump 68 provides fluid flow via line 70 to ahydraulic servoactuator assembly 72, including a servo valve 74 and afluid motor 76. The details of a suitable assembly are disclosed incopending application entitled, Hydraulic Servoactuator Arrangement foran Adaptive Steering System by the present inventor Ser. No. 21,323,filed Mar. 20, 1970.

The fluid supplied via line 70 passes through the servo valve 74 whichis of open center design with a controlled diversion of a portion of thefluid to the fluid motor 76, as described in detail in theabove-referenced application. A pressure relief 78 is provided toprevent excessive pressure demands for the fluid motor 76, so as toprovide sufficient flow for the requirements of the steering gear 80which is supplied via conduit 82, and other downstream components.

The hydraulic rate gyro is supplied via line 84 and line 26 with thereturn flow being connected to the power steering return line 86 vialine 36.

The differential pressure signal lines 54 and 56 are connected to adifferential amplifier 88, which is designed to sum the other fluidiccontrol signals, such as a vehicle speed sensor 92 together with the yawrate pressure signals and produce amplified output signals in lines 94,96 indicative of the magnitude of the need for corrective action by thefluid motor 76.

These signals are applied to the servo valve 74 which in turn providesan output motion tending to compensate for lateral disturbances in themanner disclosed in detail in the abovereferenced applications.

It will be appreciated that many variations of the above embodiment arepossible within the scope of the invention. For example, the flappernozzles may in the alternative be positioned directly opposite eachother rather than on the same side of the rotor on opposite sides of thespin axis.

From the above description, it can be appreciated that a fluid rate gyrohas been provided which is extremely simple and reliable and may beincorporated into an adaptive steering system to great advantage.

lclaim:

l. A fluid gyro comprising:

a housing:

a rotor disposed in said housing;

fluid support means for creating a rotatably fluid support for saidrotor in said housing including means providing fluid flow through atleast one clearance space between said rotor and said housing;

reaction means for creating fluid flow out of said rotor so as to causesaid rotor to spin;

fluid supply means supplying fluid to said fluid support means and saidreaction means in parallel; and

a pair of opposed fluid outlets disposed to apply parallel fluid jets atsaid rotor opposing angular movement of said rotor out of the plane ofspin; and

means for sensing the pressure upstream of said jets, and

wherein said fluid supply means also supplied fluid to said outlets,whereby the rate of angular movement is sensed by said pressure sensingmeans.

2. The gyro of claim 1 wherein said fluid outlets are connected withsaid fluid supply means in parallel with said support means and saidreaction means.

3. A fluid gyro comprising:

a housing;

a rotor disposed in said housing;

fluid support means for creating a rotatably fluid support for saidrotor in said housing including means providing fluid flow through atleast one clearance space between said rotor and said housing andfurther includes spherical complemental surfaces formed on a hub portionof said rotor and on said housing with said at least one clearance spacebeing therebetween, said hub surface being disposed inwardly of saidhousing surface;

reaction means for creating fluid flow out of said rotor so as to causesaid rotor to spin and including at least one radially directed passagein said rotor communicating with a peripheral outlet;

fluid supply means supplying fluid to said fluid support means and saidreaction means in parallel, and including a source of fluid pressureandan axial passageway in said rotor in direct communication with said atleast one clearance space, said at least one radial passage, and saidsource of fluid pressure; and

a pair of fluid outlets disposed on either side of the spin axis of saidrotor and disposed to direct fluid streams axially at said rotor,opposing angular movements thereof out of the plane of spin, whereby therate of angular movement is sensed by said pressure sensing means.

4. The gyro of claim 3 wherein said fluid outlets are connected directlyto said source of fluid pressure.

5. The gyro of claim 4 further including means for sensing the pressuredifference immediately upstream of said outlets whereby a sensing of therate of angular movement is provided.

6. A method for detecting rates of angular movement of a body inresponse to disturbances of a range of frequencies including:

mounting a gyro to said body including a housing, a rotor rotatablymounted in said housing, spinning said rotor about an axis transverse tosaid angular movements, and resiliently restraining said rotor fromangular movement relative to said housing in response to saiddisturbances by axially directing opposing fluid streams at the rotorperiphery of suflicient momentum to provide a rotor natural frequency insaid mode of angular movement substantially higher than said range ofdisturbance frequencies, and producing a signal corresponding to themovement of the rotor against the restraining effect of the fluidstreams.

1. A fluid gyro comprising: a housing: a rotor disposed in said housing;fluid support means for creating a rotatably fluid support for saidrotor in said housing including means providing fluid flow through atleast one clearance space between said rotor and said housing; reactionmeans for creating fluid flow out of said rotor so as to cause saidrotor to spin; fluid supply means supplying fluid to said fluid supportmeans and said reaction means in parallel; and a pair of opposed fluidoutlets disposed to apply parallel fluid jets at said rotor opposingangular movement of said rotor out of the plane of spin; and means forsensing the pressure upstream of said jets, and wherein said fluidsupply means also supplied fluid to said outlets, whereby the rate ofangular movement is sensed by said pressure sensing means.
 2. The gyroof claim 1 wherein said fluid outlets are connected with said fluidsupply means in parallel with said support means and said reactionmeans.
 3. A fluid gyro comprising: a housing; a rotor disposed in saidhousing; fluid support means for creating a rotatably fluid support forsaid rotor in said housing including means providing fluid flow throughat least one clearance space between said rotor and said housing andfurther includes spherical complemental surfaces formed on a hub portionof said rotor and on said housing with said at least one clearance spacebeing therebetween, said hub surface being disposed inwardly of saidhousing surface; reaction means for creating fluid flow out of saidrotor so as to cause said rotor to spin and including at least oneradially directed passage in said rotor communicating with a peripheraloutlet; fluid supply means supplying fluid to said fluid support meansand said reaction means in parallel, and including a source of fluidpressure and an axial passageway in said rotor in direct communicationwith said at least one clearance space, said at least one radialpassage, and said source of fluid pressure; and a pair of fluid outletsdisposed on either side of the spin axis of said rotor and disposed todirect fluid streams axially at said rotor, opposing angular movementsthereof out of the plane of spin, whereby the rate of angular movementis sensed by said pressure sensing means.
 4. The gyro of claim 3 whereinsaid fluid outlets are connected directly to said source of fluidpressure.
 5. The gyro of claim 4 further including means for sensing thepressure difference immediately upstream of said outlets whereby asensing of the rate of angular movement is provided.
 6. A method fordetecting rates of angular movement of a body in response todisturbances of a range of frequencies including: mounting a gyro tosaid body including a housing, a rotor rotatably mounted in saidhousing, spinning said rotor about an axis transverse to said angularmovements, and resiliently restraining said rotor from angular movementrelative to said housing in response to said disturbances by axiaLlydirecting opposing fluid streams at the rotor periphery of sufficientmomentum to provide a rotor natural frequency in said mode of angularmovement substantially higher than said range of disturbancefrequencies, and producing a signal corresponding to the movement of therotor against the restraining effect of the fluid streams.